Bulimia Nervosa is a serious eating disorder which is characterized by frequent uncontrolled eating binges. Binge Eating Disorder is a more recently described disorder which occurs primarily in obese individuals and which also carries significant morbidity. While a great deal is known about the characteristics and treatment of these disorders, particularly Bulimia Nervosa, there is as yet a limited understanding of their pathophysiology. The aim of this ongoing research program has been to rigorously describe the eating behavior of individuals with disorders of binge eating and, using this information, to generate and test hypotheses concerning their pathophysiology. Work to date has suggested that patients with Bulimia Nervosa have a disturbance in the perception of satiety which is most apparent in the later stages of the binge meal. In addition, recent studies indicate that patients with this syndrome display slowed gastric emptying and blunted postprandial CCK release. These findings are now sufficient to suggest a model of the pathophysiology of Bulimia Nervosa, and the proposed project will critically test important features of this model. One experiment will test the hypothesis that blunted postprandial CCK release is cause by delayed gastric emptying. A second biological experiment, based on reports of increased gastric capacity in Bulimia Nervosa, will examine gastric function in these patients and will assess their perception of gastric distention and reflex gastric relaxation response to a meal. This study will also address reports of elevated pain thresholds in Bulimia Nervosa, and use methods of signal detection theory to measure perceptual sensitivity and response bias to gastric distention, and thermal stimuli. This will establish whether the disturbance in satiety in Bulimia Nervosa is part of a more general sensory disturbance.